In a digitizing system of this character, a certain number of samples are taken at a given rate from a single or nonrepetitive signal. These samples are digitized and then stored in a memory for recordal and utilization.
Three main types of transient-signal digitizers can be defined.
The first type is designed to operate at a digitizing rate less than or equal to some twenty megahertz. A system of this first type includes a clock-controlled sampling device which receives the signal to be processed, an analog-digital series or series-parallel converter and a memory which stores the digitized data.
This system has a correct range which may be greater than or equal to 8 bits and a number of points limited by the memory capacity.
The second type of digitizer is able to work at a rate higher than 20 MHz.
Such a digitizer does not differ essentially from the one previously described except in the arrangement of the analog-digital converter, which is formed by a chain of comparators each biased at a voltage which corresponds to a quantization level. This chain contains as many comparators minus 1 as there are quantization levels.
Such a system has a limited dynamic range and a high weight of components.
The third known type of digitizer uses an oscilloscope with a memory.
In this case, on reception, the signal is recorded in real time in a memory mosaic similar to that of an oscilloscope. A slow sweep of television type empties the cells which were loaded by the recording and in this way produces a slow-rate digitized video signal.
Such a system offers the advantage of an apparently high sampling rate of the order of 1 GHz or more. However, the number of points is limited to a few hundred and distortions occur which can be attributed to nonlinearity in the sweep.